Structural polymeric features that contribute to in vitro immunostimulatory activity of instant coffee

[Display omitted] •Data show that instant coffee polymers stimulate both innate and acquired immune system cells in vitro.•The activity is due to the arabinogalactan rich fractions, as observed in two different brands.•These fractions stimulate in vitro B lymphocyte, macrophages and dendritic cells.•α-Chymotrypsin treatment did not affect B lymphocytes activation.•Arabinofuranosidase treatment decrease B lymphocytes activation. An instant coffee fraction, rich in arabinogalactans, obtained by ultrafiltration, using 1 and 5kDa membranes, has previously shown in vitro stimulatory activity on BALB/c mice spleen B lymphocytes. The compounds inducing lymphocytic activation were shown to elute, mainly near the void volume by size-exclusion chromatography, using Bio-Gel P6 (1–6kDa). Treatment of the compounds with chymotrypsin, a digestive protease, did not affect the induced B lymphocyte activation. On the contrary, hydrolysis with an α-l-arabinofuranosidase, removing single terminally-linked arabinose residues, decreased the extent of B cell activation. The immunostimulatory activity of these compounds was also observed by in vitro experiments, using bone marrow-derived macrophages and dendritic cells as responders. Altogether, these results show the relevance of single arabinose residues, present at the non-reducing end of polymeric compounds, to the coffee stimulatory activity in cells mediating innate and acquired immunity.